| Abstract |
The paper deals with a new soft switching system in three-phase three-level voltage source inverters.In the majority of soft switching systems applied until now, additional capacitors are connected inparallel to main transistors and very often special inductors are connected in series to auxiliarytransistors. In cases when disturbances in the control system of the voltage source inverters wouldoccur, the main or auxiliary transistors can be damaged because capacitors can be abrupt dischargedthrough the main conductive transistors or sudden interruption of the inductor current can causeovervoltages which may be dangerous for semiconductor elements. Above mentioned disadvantagesdo not occur in the proposed soft switching system and the control method of the transistor switchingis simpler in comparison to the existing soft switching systems. This paper presents switchingprinciples of all transistor of the three-phase three-level voltage source inverter, and guidelines for theselection of elements of this system are briefly discussed. The working correctness of the new softswitching system was validated during laboratory tests, and attention was also paid to certainlimitations of the control algorithm. The proposed system is recommended for medium and highpower inverters. |
